The use of inorganic resist materials to produce micron and submicron features in various substrates has been reported in the literature. The successful fabrication of such small features is of prime interest to the electronics industry in its quest for ever-finer resolution for microcircuit applications.
A particular inorganic resist system which has drawn considerable attention is silver sensitized germanium-selenide films. This resist system is formed by coating a film of germanium-selenide with a layer containing a source of silver. The silver layer is then irradiated with light or electron beam through a suitable mask resulting in selected doping of the Ge/Se film with silver by the well-known phenomenon of light-induced silver migration.
The Ge/Se film is then etched to remove the portion not doped with silver, thus leaving the doped film as a mask for further processing of the underlying substrate. Although the undoped portion of the film can be removed by wet etching techniques, it is preferable to develop it by plasma etching using carbon tetrafluoride as the etchant gas. This process yields good contrast and selectivity. The sensitivity of carbon tetrafluoride etching, however, is relatively low, a disadvantage.
In accordance with this invention, a means of etching silver-doped Ge-Se films is provided which substantially improves both sensitivity and contrast and, in addition, significantly improves selectivity in reactive sputter etching.